Device for preventing a collision between a work holder and a tool in numerical control for a turret punch press

ABSTRACT

A device for preventing a collision between a work holder (20) and a tool in numerical control equipment for a turret punch press. A region occupied by the work holder (20) in a mechanical coordinate system, is stored in a work holder region storing memory (4), and the sizes of a plurality of tool posts of a turret (24), or the sizes of tools received in the tool posts, are stored in a tool post shape storing memory (4). At the time of tool selection, a punching inhibit computing circuit (1) computes a punching inhibit region for a selected one of the tools on the basis of the stored contents of the work holder region storing memory (4) and the tool post shape storing memory (4). Immediately before the execution of a punch command, a collision preventing circuit (1) checks whether the position of the selected tool is within the punching inhibit region or not, and if so, it stops the operation of the machine.

BACKGROUND OF THE INVENTION

The present invention relates to a work holder-tool collision preventingdevice for use with numerical control equipment for a turret punchpress, with which it is possible to prevent a work holder holding aworkpiece and a tool from being broken down by a collision therebetweenwhich is caused by an accidental punching operation of the tool to thework holder due to a program error or the like.

In conventional devices of this kind it is customary that a certainregion directly specified by a limit switch, parameter setting or acommand from a command tape is set up as an axis displacement inhibitregion, thereby preventing a tool from colliding against a work holderdue to a program error or the like.

However, in the case of using the limit switch, much time is needed forproviding the switch and associated works. Also in the cases of theparameter setting and tape command, it is necessary for the operator toestablish the inhibit region in advance by computations consumingrelatively much time. Moreover, the sizes of tools which are mounted ona turret vary greatly, so that in order to minimize the inhibit regionand enlarge a punching region, it is desirable to modify the inhibitregion according to the size of the tool selected. However, this cannoteasily be done in the case of using the limit switch and in the cases ofthe parameter setting and tape command, the burden on the operator willincrease and a large storage capacity will be needed.

SUMMARY OF THE INVENTION

The present invention offers a solution to such defects of the prior artand has for its object to permit setting of an inhibit regioncorresponding to the tool being selected, by a simple operation and witha small storage capacity.

The present invention is directed to a device for preventing a selectedtool on the turret from colliding with a work holder holding a workpiecefor a turret punch press. The device of the present invention isprovided with a work holder region storing means for storing a regionoccupied by the work holder in a mechanical coordinate system; a toolpost shape storing means for storing the sizes of a plurality of toolposts of the turret; a punching inhibit region computing means, so thatat the time of tool selection, the size of the tool post in which theselected tool is housed is read out of the tool post shape storing meansand a punching inhibit region for the tool is calculated from theread-out information and the stored information of the work holderregion storing means; a punching inhibit region storing means forstoring the punching region; and a collision preventing means so thatimmediately before the execution of a punch command, it is detectedwhether the position of the tool is within the punching inhibit regionor not and, if so, the operation of the machine is stopped and an alarmsignal is generated.

With the device of the present invention, once data necessary forspecifying the region occupied by the work holder in the mechanicalsystem and information on the size of each tool post of the turret areset by the operator in a memory, an inhibit region corresponding to thesize of the tool selected, is automatically set up. Accordingly, theinhibit region corresponding to the tool selected can be established bya very simple operation. Furthermore, since the inhibit region iscomputed and stored when the tool is selected, the storage capacityneeded is small.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the arrangement of a numerically controlledmachine tool provided with the collision preventing device of thepresent invention;

FIG. 2 is a diagram for explaining a work holder and a punching inhibitregion;

FIG. 3 is a diagram for explaining the stored contents of a RAM 4; and

FIGS. 4 and 5 are flowcharts for describing the operation of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a diagram illustrating the arrangement of a numericallycontrolled machine tool equipped with the collision preventing device ofthe present invention, which comprises numerical control equipment NCand a turret punch press machine tool MC.

The numerical control equipment NC has a microcomputer 1 and peripheralcircuits interconnected via a bus 2. A ROM 3 is a memory for storing aprogram or the like necessary for the execution of predeterminedprocessing by the microcomputer 1, and a RAM 4 is a memory which hasareas for storing and calculating parameters such as data on the shapesof a work holder and tool posts and so forth. A magnetic bubble memory 5is a memory for storing an NC command program. Reference numeral 6indicates a manual data input device (MDI), which has various keys. Thedata on the shapes of the work holder and the tool posts are entered viathe MDI 6. Reference numeral 7 designates an interface between thenumerical control equipment NC and an electric power control circuit 8.Various information such as a punch command, a tool exchange commandincluding the number of a tool to be exchanged, an alarm signal and soon for the turret punch press machine tool MC is sent via the interface7 to the electric power control circuit 8, which performs control for atool exchange through sequence control in a known manner. Referencenumeral 9 identifies a known X-axis position control circuit providedwith an error register, a servo amplifier, etc. and 10 a Y-axis positioncontrol circuit. The output of the X-axis position control circuit 9 isconnected to an X-axis motor (not shown) which shifts a table 20 of themachine tool MC in the X-axis direction, and the Y-axis postion controlcircuit 10 is connected to a Y-axis motor (not shown) which drives thetable 20 in the Y-axis direction.

The turret punch press machine tool MC has the table 20 movable by theX-axis and the Y-axis motor to a desired position in the horizontaldirection, a work holder 22 for fixing a workpiece 21, such as a steelplate, on the table 20 and a turret 24 mounted on a column 23 in amanner to be rotatable in a horizontal plane. The turret 24 has aplurality of tool posts for receiving various tools. Provided above theturret 24 is a press mechanism 25 which responds to a punch command tostrike, from above, a tool held in a selected one of the tool posts ofthe turret 24. Usually two such work holders 22 are employed, by whichthe workpiece 21 placed on the table 20 is pressed against it fromabove.

Provided that two work holders 22a and 22b occupy, for example, thehatched regions shown in FIG. 2, data specifying each of these regionsis set by preprocessing, as a parameter, in a certain area of the RAM 4via the MDI 6. When the two work holders 22a and 22b are identical inshape, for instance, their length dL and width dw and X-axis coordinatevalues l₁ and l₂ of their centers of gravity P₁ and P₂ are used as thedata. When the centers of gravity P₁ and P₂ are not on the X-axis unlikein the illustrated example, Y-axis coordinate values of the centers ofgravity P₁ and P₂ are also input.

Upon completion of inputting this data, the microcomputer 1 computesfrom the data the hatched regions occupied by the work holders 22a and22b, and then stores them in the memory 4. FIG. 3 is a diagram showingan example of the stored contents of the RAM 4, wherein are stored theregion of the work holder 22a, X₁ ≦22a≦X₂, Y₁ ≦22a≦Y₂, and the region ofthe work holder 22b, X₃ ≦22b≦X₄, Y₁ ≦22b≦Y₂, calculated from the datadw, dL, l₁ and l₂.

Moreover, in preprocessing, the radii R01 to R24 of tool posts P01 toP24 of the turret 24 are detected and introduced via the MDI 6corresponding to tool numbers T01 to T24 which are received in the toolposts, and they are stored as parameters in the RAM 4, as depicted inFIG. 3.

In the case of starting the machining operation after storing such datain the RAM 4, when a tool exchange command is carried out, themicrocomputer 1 sends the tool number and the tool exchange command viathe interface 7 to the electric power control circuit 8, causing it tocontrol a tool select operation. At the same time, the microcomputer 1calculates, from the work holder region data and the tool post shapedata corresponding to the tool number of a selected tool (both stored inthe RAM 4), a punching inhibit region of the tool and stores it in theRAM 4, as shown in FIG. 4. For instance, when the radius of the toolpost of the selected tool is R01, a region 22ap which is represented byX₁ -R01≦22ap≦X2+R01, Y₁ -R01≦22ap≦Y₂ +R01 is computed as a punchinginhibit region for the work holder 22a and a region 22bp which isrepresented by X₃ -R01≦22bp≦X₄ +R01, Y₁ -R01≦22bp≦Y₂ +R01 is computed asan punching inhibit region for the work holder 22b. Incidentally, itwould be more appropriate to set up the punching inhibit regions withinregions (indicated by 22ap' and 22bp' in FIG. 2) spaced R01 apart fromthe work holders 22a and 22b, but a complex computing process isrequired.

FIG. 5 is a flowchart showing the contents of a process which isexecuted by the microcomputer 1 in response to a one-block command.

As is known in the art, the microcomputer 1 interprets an NC commandprogram, block by block, computes X-axis and Y-axis command values Pxand Py, by way of pulse distribution, from a given amount and speed ofmovement of the table, and provides them to the X-axis and Y-axisposition control circuits 9 and 10, respectively. Next, the currentcommand values Px and Py are added to an accumulated value X₀ of theprevious command values, thereby updating the coordinate position of thetable. Next, it is checked whether the table has reached the punchingposition. If not, the table moving process is continued. If the punchingposition has been reached, it is checked whether the current coordinateposition (the center position of the tool) is within the punchinginhibit region of the selected tool set in the RAM 4. If not, a punchcommand is provided via the interface 7 to the electric power controlcircuit 8 to cause it to activate the press mechanism 25, performing apunching operation. When the center position of the tool (which is thesame as the updated coordinate position) lies within the punchinginhibit region, an alarm signal is sent via the interface 7 to theelectric power control circuit 8, by which an alarm lamp or buzzermounted on a panel of the machine or the like is lighted or sounded, anda process for suspending the machining operation is carried out.

While in the above embodiment the length dL and width dw of each of thework holders 22a and 22b and the X-axis coordinate values l₁ and l₂ oftheir centers of gravity are used as the data for specifying theirshapes, it is also possible, of course, to specify their shapes by usingother data. Provision may also be made for computing the region occupiedby the work holder and the punching inhibit region at the time of acommand for selection of a tool, instead of computing the regionoccupied by the work holder and storing it in the RAM 4 prior to thestart of the machining operation. It is also possible to set the innerdiameter of each tool post. Moreover, for strictly setting the range ofthe inhibit region, it is desirable to compute it from the maximumdiameter of the tool, but it is cumbersome to measure the maximumdiameters of tools having special shapes other than round and squareones. The foregoing embodiment is adapted to set the size of each toolpost, noting that it is always somewhat larger than the maximum diameterof the tool. Also in the cases of tools with special shapes, however, itis all right to measure and set their maximum diameters.

As described above, according to the present invention, once datanecessary for specifying the region occupied by the work holder andinformation on the size of each tool post of the turret or the size ofeach tool are set in a memory, an inhibit region corresponding to thetool to be selected, is automatically set. Accordingly, an inhibitregion well suited to the selected tool can be set by a very simpleoperation. Furthermore, since the inhibit region corresponding to theselected tool is computed and stored when selecting the tool, thestorage capacity used may be small. Besides, when the inhibit region isset as an axis displacement inhibit region, some limitations may beimposed on the path from a certain machining point to the next. In thepresent invention, however, since the inhibit region is set as apunching inhibit region, not as the axis displacement inhibit region,such a disadvantage will not be encountered.

What is claimed is:
 1. A device for preventing a collision between awork holder and a tool in numerical control equipment for a turret punchpress, comprising:work holder region storing means for storing datarepresenting a region occupied by the work holder in a mechanicalcoordinate system; tool post shape storing means for storing datarepresenting the sizes of a plurality of tool posts of a turret or thesizes of tools received in the tool posts; punching inhibit regioncomputing means for reading out the size of the tool post receiving theselected tool or the size of the selected tool from the tool post shapestoring means at the time of tool selection, and for computing apunching inhibit region for the selected tool from the read-outinformation and the stored information of said work holder regionstoring means; punching inhibit region storing means for storing thepunching inhibit region; and collision preventing means for checkingwhether the position of the selected tool is within the punching inhibitregion or not immediately before the execution of a punch command, andfor stopping the operation of the machine and generating an alarm signalif the position of the selected tool is within the punching inhibitregion.
 2. A device for preventing a collision between a work holder anda tool in numerical control equipment for a turret punch press,comprising:means for storing first data representing a region occupiedby the work holder and second data representing the shapes of toolposts; and a central processing unit for computing a punching inhibitregion for a selected tool at the time of tool selection based on thefirst and second data and for checking whether the position of theselected tool is within the punching inhibit region or not immediatelybefore the execution of a punch command, said central processing unitstopping the operation of the turret punch press and generating an alarmsignal if the position of the selected tool is within the punchinginhibit region.
 3. A method for preventing a collision between a workholder and a tool in numerical control equipment for a turret punchpress, comprising the steps of:(a) storing first data representing aregion occupied by the work holder; (b) storing second data representingtool post shapes; (c) automatically computing a punching inhibit regionfor a selected tool based on the first and second data at the time oftool selection; (d) checking whether the position of the selected toolis within the punching inhibit region or not immediately before theexecution of a punch command; and (e) stopping the operation of theturret punch press and generating an alarm signal if the position of theselected tool is within the punch inhibit region.